Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 301408
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST SAT AUG 30 2014

.SYNOPSIS...
GENTLE TRADE WINDS WILL PREVAIL ACROSS THE ALOHA STATE THROUGH THE
LABOR DAY HOLIDAY WEEKEND. THESE LIGHTER WINDS WILL ALLOW LOCAL
SEABREEZES TO DEVELOP ACROSS MOST INTERIOR AND LEEWARD SECTIONS EACH
AFTERNOON...PRODUCING LOCALIZED CLOUD BUILDUPS AND SOME SHOWERS.
LOCAL LAND BREEZES WILL BRING CLEARING SKIES OVER THESE SAME AREAS
AT NIGHT. THE WEAK TRADE WINDS WILL CONTINUE TO CARRY SOME LOW
CLOUDS AND BRIEF SHOWERS INTO WINDWARD AND MAUKA AREAS...ESPECIALLY
NIGHTS AND MORNINGS. A MORE TYPICAL TRADE WIND WEATHER PATTERN MAY
RETURN TO THE ISLANDS BY THE MIDDLE OF NEXT WEEK.

&&

.DISCUSSION...
THE PRESSURE GRADIENT SOUTH OF A 1025 MB SURFACE HIGH NEAR 40N
160W... OR ABOUT 1300 MILES NORTH OF HONOLULU... CONTINUES TO
MAINTAIN THE LOW-LEVEL TRADE WIND FLOW ACROSS THE ALOHA STATE EARLY
THIS MORNING. THIS HIGH IS MOVING TOWARD THE EAST NORTHEAST AT ABOUT
10 MPH. THE REMNANT SURFACE TROUGH ASSOCIATED WITH FORMER
NORTHEASTERN PACIFIC TROPICAL CYCLONE LOWELL...WHICH IS LOCATED
ABOUT 700 MILES NORTH OF HILO...IS MOVING WESTWARD AT ABOUT 10 MPH.
SATELLITE IMAGERY ALSO INDICATES THERE IS A SMALL LOW CLOUD SWIRL...
APPARENTLY DENOTING A WEAK LOW-LEVEL TROUGH...CENTERED ABOUT 100
MILES DUE EAST OF HANA. THIS FEATURE IS MOVING WESTWARD AT ABOUT 10
MPH.

LOOPS OF WATER VAPOR IMAGERY SHOW AN EAST NORTHEAST TO WEST
SOUTHWEST ORIENTED UPPER TROPOSPHERIC RIDGE IN THE VICINITY OF THE
BIG ISLAND. IN ADDITION TO THIS FEATURE...THERE IS SIGNIFICANT
SUBSIDENCE HIGH ABOVE MOST OF THE ISLANDS. THE PRESENCE OF THE
RIDGING AND THE SINKING AIR ALOFT ARE MAINTAINING STABLE ATMOSPHERIC
CONDITIONS ACROSS THE MAIN HAWAIIAN ISLANDS THIS MORNING. THE
PRECIPITABLE WATER VALUES RANGED FROM 1.4 INCHES AT LIHUE TO ABOUT
1.1 INCHES AT HILO IN THE BALLOON SOUNDINGS...WHICH WERE COMPLETED A
COUPLE OF HOURS AGO. ALSO...AN ABOVE NORMAL TRADE WIND INVERSION OF
AROUND 10 THOUSAND FEET CONTINUES IN THE SOUNDING FROM LIHUE.
HOWEVER...THE LOW-LEVEL INVERSION APPEARS TO HAVE DROPPED TO AROUND
8 THOUSAND FEET AT HILO...WHICH IS CLOSER TO THE UPPER LEVEL RIDGE.

THE FORECAST MODELS INDICATE THE SUBTROPICAL HIGH WILL REMAIN RATHER
WEAK AND FAR TO THE NORTH OF THE AREA THROUGH THE LABOR DAY HOLIDAY
WEEKEND. IN ADDITION...THE SURFACE TROUGH ASSOCIATED WITH THE
REMNANTS OF LOWELL WILL REMAIN NORTH OF THE ISLANDS AT LEAST THROUGH
TONIGHT. ALSO...THE LOW CLOUD SWIRL EAST OF MAUI WILL LIKELY REMAIN
IN THE VICINITY OF THE ISLANDS FOR THE NEXT 12 TO 18 HOURS. THE
PRESENCE OF THIS LOWER PRESSURE TO THE NORTH OF AND NEAR THE ISLANDS
SHOULD CAUSE A SLACKENING OF THE PRESSURE GRADIENT. AS A RESULT...WE
EXPECT THE TRADE WIND SPEEDS WILL CONTINUE TO WEAKEN. AT THE SAME
TIME...THE UPPER LEVEL RIDGING NEAR THE ISLANDS SHOULD MAINTAIN A
RELATIVELY STABLE ATMOSPHERIC REGIME OVER THE STATE.

THE LIGHT TO GENTLE TRADE WINDS ARE EXPECTED TO PRODUCE A DIURNAL
CONVECTIVE PATTERN OF LOCAL AFTERNOON SEABREEZES AND NIGHTTIME
LANDBREEZES THIS WEEKEND. THIS WEATHER PATTERN TYPICALLY PRODUCES
LOCALIZED CLOUD BUILD UPS WITH ISOLATED SHOWERS ACROSS MANY INTERIOR
AND LEEWARD AREAS OF THE ISLAND CHAIN EACH AFTERNOON. AT THE SAME
TIME...THE WEAK LOW-LEVEL TRADE FLOW WILL CONTINUE TO TRANSPORT SOME
LOW CLOUDS AND BRIEF SHOWERS INTO THE WINDWARD FACING SLOPES AND
HIGHER TERRAIN...ESPECIALLY DURING NIGHTS AND EARLY MORNINGS. AT
NIGHT...THE LAND BREEZES SHOULD CLEAR SKIES OVER MOST OF THE
REMAINDER OF THE SMALLER ISLANDS. NOTE THAT THE ARRIVAL OF THE SMALL
LOW CLOUD SWIRL MAY PROVIDE SOME LOCAL INCREASE IN MOISTURE OVER
SOME OF THE ISLANDS LATER TODAY AND THIS EVENING.

THE GENTLE TRADE WIND WEATHER PATTERN WILL LIKELY CONTINUE AT LEAST
THROUGH LABOR DAY. THE FORECAST MODELS APPEAR TO INDICATE THE TRADE
WINDS MAY RETURN TO MODERATE SPEEDS DURING THE MIDDLE AND LATER PART
OF NEXT WEEK. THIS WILL LIKELY BRING A RETURN TO A MORE TYPICAL
TRADE WIND WEATHER PATTERN ACROSS THE STATE.

&&

.AVIATION...
LIGHT TRADES ARE EXPECTED TO CONTINUE TODAY...WITH SOME LOCAL
AFTERNOON SEA BREEZES POSSIBLE. PREDOMINANTLY VFR CONDITIONS ARE
EXPECTED...HOWEVER CLOUDS AND SHOWERS RIDING IN ON THE TRADES COULD
BRING BRIEF MVFR CONDITIONS TO THE WINDWARD AND MOUNTAIN AREAS. NO
AIRMETS ARE IN EFFECT.

&&

.MARINE...
ABOVE NORMAL SURF PRODUCED BY THE CURRENT SOUTH SWELL CONTINUES TO
REQUIRE A HIGH SURF ADVISORY ALONG SOUTH FACING SHORES OF THE MAIN
HAWAIIAN ISLAND CHAIN THIS MORNING. THE BARBERS POINT BUOY CONTINUES
TO SHOW A SIGNIFICANT WAVE HEIGHT OF ABOUT 4 FEET WITH A PERIOD OF
13 TO 14 SECONDS FROM AN AZIMUTH OF 180 TO 190 DEGREES. GUIDANCE
FROM THE WAVE WATCH III MODEL SUGGESTS THIS ELEVATED SURF WILL
CONTINUE THROUGH TONIGHT. AS A RESULT...THE HIGH SURF ADVISORY
REMAINS IN EFFECT UNTIL 6 AM HST SUNDAY MORNING. LOOKING AHEAD...
ANOTHER REINFORCING SOUTH SWELL IS FORECAST TO ARRIVE ON SUNDAY. YET
ANOTHER VERY LONG-PERIOD SOUTH SWELL ARRIVING TUESDAY WILL GRADUALLY
BUILD THROUGH WEDNESDAY. AS A RESULT...SURF MAY REMAIN NEAR OR ABOVE
THE HIGH SURF ADVISORY THRESHOLD ALONG SOUTH FACING SHORES OF THE
ISLANDS THROUGH THE MIDDLE OF NEXT WEEK.

THE LIGHT TRADE WINDS WILL KEEP WINDS WELL BELOW THE SMALL CRAFT
ADVISORY CRITERIA INTO EARLY NEXT WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST SUNDAY FOR SOUTH FACING SHORES OF
NIIHAU...KAUAI...OAHU...MOLOKAI...LANAI...KAHOOLAWE...MAUI  AND THE
BIG ISLAND.

&&

$$

DISCUSSION/MARINE...HOUSTON
AVIATION...MBALLARD





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